In short. Ceramides, glycerin, occlusives, urea and lactic acid as categories: what each one does, which symptom it answers, and what has not earned a place.
Key points
- Tightness within minutes of washing answers to a humectant.
- Flaking and roughness answer to an emollient and the occlusive over it.
- Skin short of barrier lipids answers to ceramides.
A moisturiser does three jobs, and the ingredients divide further. Here is the short list that earns a place in a routine for dry skin, and the symptom each one answers.
Ceramides: replacing part of what is missing
Ceramides are among the lipids sitting between the cells of the outer layer, and the ones most reduced in dry and eczematous skin. A product that supplies them is topping up a mortar that has thinned. The effect builds over weeks rather than appearing on the first evening, and it is largest in skin genuinely short of barrier lipids.
Glycerin: the humectant with the most behind it
Glycerin draws water into the outer layer and holds it there, and it is the humectant studied longest. It makes a product feel comfortable within minutes rather than merely coated. Used alone in very dry air it can pull water from below rather than from the air, which is why it almost always appears with something that seals over it.
The occlusives: what holds the water in
Petrolatum, mineral oil, dimethicone and the simpler waxes form a layer that slows evaporation, and this group does the measurable work. The trade is unavoidable: the more effective the occlusive, the heavier it feels. Use the heavier end at night and on the hands, and the lighter end during the day.
Match the ingredient to the symptom
Tightness within minutes of washing answers to a humectant. Flaking and roughness answer to an emollient and the occlusive over it. Skin short of barrier lipids answers to ceramides. Itching from a dry surface answers to any of them used often enough, and to none of them used once.
Urea and lactic acid: two that do more than one job
Both hold water, and both loosen the bonds between surface cells as the strength rises, which is why they are used where skin has thickened or scaled. On the shins, the heels and the upper arms they often do what a plain cream cannot.
What has not earned its place
Fragrance is the commonest reason a product irritates skin short of a barrier, and it is added for the nose, not the skin. Denatured alcohol gives a light feel and dries the surface. Essential oils and the newer peptide and growth-factor names sit in the same category as far as holding water in is concerned: no established role. None is dangerous in healthy skin, and all are avoidable in skin that is already stinging.
What to leave out of the routine
- Fragrance, essential oils and denatured alcohol, on skin that is tight or stinging.
- Exfoliating acids used in the same weeks as a prescription topical.
- Urea or lactic acid on cracked skin, or on a face that is already irritated.
What sits above these on the ladder is set out in prescription and procedure options, and how a routine holds once it is working is in maintenance, and when dry skin needs no treatment.
Frequently asked questions
Do I need ceramides in a moisturiser if my dryness is mild?
Probably not, and it is not the first thing to spend on. Ceramides matter most in skin that is genuinely short of barrier lipids, which usually means eczema, very dry older skin, or skin that has been stripped for a long time. For mild seasonal dryness, a plain occlusive applied to damp skin does more than a ceramide product applied to skin that has already dried.
Why does urea sting on cracked skin but not on intact skin?
Because of its second action. At the strengths used for thickened or scaly skin, urea loosens the bonds between surface cells, and on intact skin that is felt as nothing at all. On skin that has cracked or split, the same effect reaches nerve endings that are no longer covered, and it registers as stinging. If it stings, the answer is to stop rather than to persist.
Is glycerin enough on its own in a dry climate?
Not usually. Glycerin draws water towards the skin and needs water to draw on, and in very dry air it may take that water from the deeper skin rather than from the air. That is why it is nearly always combined with something that seals over it. In a heated room or an air-conditioned office, the sealing half of the product is the half doing the work.
Risks & Limitations
- A moisturiser slows water loss from the skin. It does not add water to skin that is short of it, and it does not treat a skin disease.
- No cream treats eczema, psoriasis, thyroid disease or diabetes. Those need a diagnosis and usually prescription treatment.
- Skin that is red, warm and itchy is inflamed rather than dry, and a heavier moisturiser delays the treatment it needs.
- A routine works only while it is used. Dry skin is managed rather than cured, and stopping the routine brings the dryness back.
When to Seek Care
- A rash with fever, blistering, swelling of the face or lips, or sores in the mouth needs care the same day.
- Generalised itching with weight loss, night sweats, or a medicine started in recent weeks.
- Dryness with tiredness, weight change, thirst, or joints that are stiff and painful.
- Skin that is cracked, weeping or crusted, or a dry mouth together with dry eyes.
References & Further Reading
- American Academy of Dermatology (AAD) — guidance on dry skin, eczema and psoriasis
- International League of Dermatological Societies (ILDS) — clinical guidance
- National Institute for Health and Care Excellence (NICE, UK) — guidance on eczema and dry skin
- Cochrane Library — systematic reviews
- Chinese Medical Association Dermatology Branch — clinical guidance
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.